Economizer hvac and control system

ABSTRACT

An HVAC and control system with an economizer mode and continuous damper position verification. Three dampers are provided with a control module that accepts inputs from multiple temperature sensors and a user, and which monitors and reports the position and off-normal operation of multiple dampers.

PRIORITY/CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/654,561, filed Jun. 1, 2012, the disclosure of which is incorporated by this reference.

BACKGROUND

The disclosure generally relates to the field of heating, ventilation, and air conditioning (HVAC) systems. In the world of HVAC, cooling is provided when heat in the air within a conditioned space (such as the interior of a building) is removed by circulating the air through a cooling coil (i.e., an “air conditioner”) and then re-delivered to the conditioned space to keep the space at the desired temperature. Some HVAC systems have an economizer, which is a subsystem that introduces outside air into the building when the outside air is cool enough that it can be used to either supplement or replace mechanical cooling. An HVAC system with an economizer typically has a set of three actuator-driven dampers. Dampers are devices that function to regulate airflow within an air duct by closing or opening in the duct, to stop or allow air flow in the duct.

When an HVAC system operates in economizer mode, one damper is closed to isolate the duct leading from the conditioned space to the indoor blower, which circulates air in the HVAC system. This is done to interrupt the flow of air from the conditioned space, or return air, so that it is not circulated through the cooling coil and resupplied to the conditioned space. At the same time, a separate damper is opened in a connecting air duct, which allows outside air to be pulled into the system. A third damper is also often used to relieve air from the conditioned space so that new air introduced from the outdoors does not overly pressurize the conditioned space.

During economizer-supported cooling, the compressor of the HVAC system may be stopped if outdoor air conditions are sufficient to provide space cooling. This is generally called free cooling. If the outdoor air is insufficient to provide cooling by itself the compressor is allowed to run while dampers are configured for economizing and in this way outside air can supplement compressor operation. This is often called enhanced economizer operation or economizer-supported mechanical cooling.

The theory behind economizer systems is that cool outside air may be circulated throughout a building to provide cooling in a conditioned space, with the goal of saving money by reducing the need to run more energy-intensive mechanical (i.e., compressor-based) cooling. In practice, however, an estimated 64% of economizer installations do not function properly. In fact, some economizer systems function improperly from the day they are installed. These problems can go unrecognized for years, and the economizer may not be providing a benefit at all. Instead, the economizer may be causing the HVAC system to use even more energy than it otherwise would because the HVAC system operates to support both cooling and heating of uncontrolled outside air.

Often, an economizer system functions improperly because of malfunctioning dampers, which may be from improper installation, mechanical problems, control issues, or normal wear. Damper malfunctions include situations when a damper is disconnected from system control, control cabling is cut or broken, seizes or otherwise fails to move when directed to do so. While damper malfunction is a large problem, it is the lack of detection of this problem that causes energy to be wasted. If a damper is stuck open or shut, the building owner is typically unaware of the error condition. But the economizer system, and thus the HVAC system, is functioning improperly, thereby contributing to higher costs of HVAC system operation.

BRIEF SUMMARY

The disclosed technology is an HVAC system and control module with an economizer function. The HVAC system and control module utilizes dampers that have sensors that send signals indicating when the damper is in either a closed or open position. The system monitors the dampers and the economizer function and displays system information to a user. The system verifies that the dampers are in the correct positions required to support either economizing or non-economizing operation. Certain systems could operate with a partially open damper, and offer verification of proper damper position.

The disclosed technology is an HVAC system and control module which has a power source, a circulation fan, an air conditioning compressor, a network of air delivery ducts for delivering cool air to a conditioned space, such as interior space in a building. The system includes an outside air intake duct and a first damper, also called the outside air damper. The intake damper is movable between an open and closed position and the damper includes two sensors which detect if it is in the open or closed position. No other split-system economizer provides two sensors of damper position. (Definition—A split-system air conditioning system is one in which air circulates in a closed loop.) The damper position sensors send a signal to a control module in the conditioned space, which indicates to the user by a visible indicator if the intake damper is in the fully open or fully closed position, or if the damper has failed to achieve the correct position for the selected mode.

The disclosed technology includes an outside air sensor, which can take the form of a thermostat. Economizer operation is activated when the outside air temperature falls below the setting chosen on an outdoor air thermostat.

In another version an outdoor temperature sensor is used; a calculation performed by the controller generates a minimum outside air temperature target, and if the outside air temperature reaches the set minimum temperature, then an economizer mode is activated.

In the economizer mode, the intake damper is opened and outside air is drawn into the ducting of the system. Two position sensors on the intake duct verify that the damper position is correct for the economizer mode; if the damper is in an incorrect position, a visual indicator is activated at the control module.

The control module of the system is mounted in the conditioned space. The control module has a damper error indicator which is a visual indicator of some type such as a light or an indicator on a display. Having a control module for the damper located in the conditioned space, and having the control module display a visual error indicator is a critical improvement of the disclosed technology. Besides an error indicator, the control module can display an indicator that the economizer mode is activated and working properly, and other information to the user.

The control module in the disclosed system also has a non-economizer mode which is the normal mode for the HVAC system when the economizer mode is not activated. In the non-economizer mode, the first damper is closed to prevent outside air from entering the HVAC system when the economizer mode is not selected. The non-economizer mode is automatically selected when the outside air temperature is sensed as being above the pre-selected temperature or it may be activated based on pre-selected parameters set by the user, or by manual selection of the non-economizer mode.

The control system of the disclosed technology can also include an economizer fail-safe signal, which is activated when an off normal damper position is detected. The system then attempts to allow the system to run in non-economizing mode. When the fail-safe signal is generated, the economizer mode will be turned off and the non-economizing mode activated. All embodiments prevent continued use of an economizer mode when dampers are in a fault condition, such as when the intake damper is in the wrong position for the economizer mode. This would stop the incorrect running of the economizer mode even if the operator of the system is not aware that the error had occurred. All embodiments also prevent non-economizing mode operation if dampers are not identified in the proper position to support non-economizing operation.

Another version of the disclosed technology is one which includes an inside air temperature sensor, which is used to activate the economizer mode by a comparison of the inside temperature and outside temperature, with the control module making a calculation as to when the outside air is sufficiently cooler than the inside air to be productive to introduce into the cooling system.

The control module is operationally connected to the power source, the circulation fan and the compressor relay of the HVAC unit. It is also connected to the outside air temperature sensor, and to the first damper.

Although the disclosed technology can operate with one damper, other versions of the system operate with two or three dampers. In versions in which two dampers are present, the isolation damper is in the ducting between the conditioned space and the circulation fan, and closes off the air from the conditioned space from going back to the cooling unit. In place of this re-circulated air, outside air is admitted through the first damper and is delivered to the conditioned space through the HVAC system fan. In installations in which a third damper is part of the system, the third damper is provided to open to prevent an over pressurization of the conditioned space. The third damper may not be required in some installations because there may be sufficient leakage of air to make over pressurization not possible. The leakage of air would occur when cool air is blown into the conditioned space and some of that cool air leaks around doors, windows, spaces in walls and attic, and ducted exhaust such as kitchen and bathroom exhaust vents.

An important improvement in the disclosed technology is in the cabling between the control module and other parts of the control system, particularly the dampers. The prior art installation of such a system requires a technician to run wires between a control module and the dampers, as well as the power source and the circulation fan and cooling unit and the outside temperature sensor. In prior installations, the control module is often located at the blower unit in a mechanical space and is not useful to the user, and must be serviced by a technician in tight quarters. The damper cable installation can amount to as many as 26 wire segments needing to be properly terminated at different places on the control module and to the dampers and damper status switches in the system. As many as 21 of these terminations would need to be made in the attic where temperatures may exceed 150 degrees Fahrenheit. If any one of them is connected to the wrong place, the system will not function. To avoid this complexity it is common practice to minimize the number of conductors required. Damper position sensors are typically not installed for this reason. Complexity of installation of damper status has in the past been prohibitive to its use.

The complexity problem is addressed in the disclosed technology by a connection methodology that eliminates technician effort and greatly simplifies the way the system is installed. Each of the control cables have a first end and a second end, with the first end connecting to the control module and the second end connecting to one of the required system components, which are the furnace control board, the dampers, and the external temperature sensor. Each of the cables are terminated with a fitting which is geometrically coded so that it only fits in one receptacle in the control module, and it can only fit in the fitting in one orientation. For this reason, each of the cables can only fit in the control module in the proper interfitting connection and only one orientation of the fitting is possible this reduces the potential for termination errors by one half. This feature alone makes the disclosed technology much more fool proof and economically efficient to set up.

The damper cable is particularly prone to errors during installation if it is left to a technician to make all the connections for proper operation in a difficult environment. In connecting the control module to each damper, for instance, there are power connections to the damper motors, there are connections to the position sensors of the damper, and connections in between damper switches creating the circuit that provides status logic. This typically results in the need to connect twenty six wires and if any one of them is connected to the wrong attachment point the system will be in error. This is one of the reasons why prior art of economizer systems have such a high error rate. Not only does the use of geometrically coded and pre-wired cables guarantee that the system is set up correctly, but it also enables errors in the damper positioning to be detected and reported to the user in the conditioned space, and greatly reduces the amount of time a technician spends in the hot environment of an attic. Each of these are features which are not found in the prior art.

The system also comprises a means of shutting down the economizer function when it is not functioning as intended. In one such embodiment the HVAC system operates exclusively with mechanical cooling. When an error condition of the intake damper is detected, the unit will stop operation, or only allow non-economizing operation if it can be done safely. For example if a system outside air temperature low limit sensor is installed, the outdoor air temperature would need to be above the limit setting in order for the readiness status signal to indicate that conditions are suitable, “ready” for outdoor air to be brought into the conditioned space. (Typical safety conditions would include outdoor air temperature high and low limits, outdoor humidity, outdoor dewpoint, or outdoor CO level.

The disclosed system can also operate with other sensors within the conditioned space, and intake of outside air can be based on conditions other than temperature. Sensors can include sensors for CO2, CO, formaldehyde, radon, particulates, VOCs, and other hazardous air components. For instance if a high level of CO was sensed, the system can activate the economizer mode regardless of temperature, in order to dilute and flush out the air in the conditioned space.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an HVAC system with the disclosed economizer control system.

FIG. 2 is a view of a damper in the open position.

FIG. 3 is a view of a damper in the closed position.

FIG. 4 is a view of a geometrically coded connection and the plug in on the control module.

FIG. 5 is a control diagram of the disclosed economizer control system.

FIG. 6 is a diagram showing the control logic of the disclosed economizer control system.

DETAILED DESCRIPTION

FIG. 1 shows the HVAC system of the disclosed technology, which provides for economizer mode operation of the HVAC system 10. The HVAC system 10 includes a circulation fan 12, cooling unit 14, and a network of air delivery ducts 16. The HVAC system 10 provides heating and cooling for a conditioned space 18. A user controls the economizing portion of the HVAC system 10 with control module 20. The HVAC system 10 includes an outside air intake duct 22 to provide outside airflow 24 to the conditioned space 18. Also included is a first, or intake, damper 26. The first damper 26 has two positions: a first, or closed, position 28, and a second, or open, position 30. The HVAC system 10 may have an isolation damper 32, operable between an open position 34 and a closed position 36, and a third (relief) damper 38, operable between a closed position 42 and an open position 40. A preferred embodiment of the control system and HVAC system uses three dampers. Both the second (isolation) damper 32 and the third (relief) damper 38 are located in a return air duct 44 between the conditioned space 18 and the cooling unit 14.

The control module 20 has inputs from outside air temperature sensor 46, from inside air temperature sensor 48 (optional), and includes a user input means and display screen (optional). In one embodiment a user may set the HVAC system 10 to automatically provide free cooling, economizer-supported mechanical cooling, or both. In all instances, a user may completely override any automatic control, providing for manual control of the economizing system 10. The control module also can receive inputs such as outside air temperature, outdoor humidity, outdoor dew point, or outdoor CO level, and assess high and low limits on such factors to generate a readiness signal which can disallow start of the economizer mode.

The control module 20 is connected to the essential components of the system by cables, with one end of the cables terminated by connectors which are shaped to fit in only one place in the system, and to fit in that one place in only one orientation. These terminals are referred to as “geometrically coded” because they can only fit in one place in the system, and in only one orientation. Thus the control module is connected to the dampers by a damper cable 50. The control module is connected to the outside temperature sensor 46 by an outside sensor cable 52. The control module is connected to a power source by a power cable 54. The control module is connected to the furnace control board by a furnace cable 56. Control module 20 may be connected to an inside temperature sensor 48 by an inside sensor cable 58.

The damper cable 50 preferably has four connectors, (3 damper connections and one for the control module,) and includes a circuit that would be prohibitive to fabricate and terminate in the field. The system feature of supporting damper position information is only possible if a pre-assembled damper cable is provided with geometrically coded terminations. The damper cable 50 eliminates 26 field terminations which would require over an hour to make, and allows these same connections to be made by 3 snap connectors in the attic, and one at the control module, which take less than a minute to connect. Cables connecting the furnace, and power source also replace a required 9 terminations in the field which would take at least 20 minutes.

Makes possible a very fast and 100% correct installation of all conductors needed to support damper operation and damper error detection. Connecting the cable requires attaching four “Quick Connect” connectors. One of the connectors being unique to the board, the other three connectors being interchangeable. Making these connections takes less than one minute, and is impossible to do incorrectly.

The damper cable also reduces production cost in that it allows the product to use two series circuits to determine proper damper operation for three dampers. The typical way this would be accomplished would be to use twelve wires; two for each damper switch. The damper cable provides two series circuits with a single common that work in unison with a single relay on the circuit board. This vastly simplifies the task of determining if dampers are operating properly. Damper verification is an extremely important aspect of the disclosed technology and its marketing. This feature has not been offered in the past because it is too complex for field termination, and too expensive to provide with a conventional configuration. We solved both problems.

Without the disclosed prefabricated damper cable, installers would be required to make 38 field connections, (26 terminations and 12 splices.) Just on this one cable. Without the quick connect installation time would be increased by more than an hour and would have a high probability of having been done incorrectly.

While other cables included in the disclosed system are simpler, using them reduces a further 9 connections to two additional “Quick Connects.” In one embodiment two ends of one quick connect cable reduce terminations by 23 connections. Each termination being another opportunity for error, the “Quick Connects” provides a distinct advantage in the disclosed technology, and contributes to market acceptance of a new product that might be otherwise considered too complicated and therefore unworkable.

The damper cable is in itself is more akin to a circuit board having multiple logic paths making up a circuit than it is a bundle of straight-through conductors having a single connector at each end. The damper cable contains both series and parallel circuits, the series circuits being switched by sensing devices at each damper. It also contains circuitry that enables the use of a diagnostic tool that is not covered in this patent. In its absolute simplest form, supporting only a single first damper, a technician would need to make 12 terminations all needing to be performed correctly in order for the system to operate properly.

In one embodiment the HVAC system 10 may provide outside airflow 24 into the conditioned space 18 when the outside air temperature is sufficiently lower than inside air temperature thereby providing economizer-supported mechanical cooling. In the economizer mode, the first damper 26 is in the second or open position 28, and outside air 24 is drawn into the ducting network 16. In two or three damper systems, the isolation damper 32 is in the closed position 36, and the third damper 38 is in the open position 40. The HVAC system 10 then circulates outside air such that the HVAC output flow 60 is comprised of outside air. The isolation damper 32 operates with the first damper 26 in a coordinated fashion such that when the first damper 26 is open, the isolation damper 32 is closed, and when the first damper 26 is closed, the isolation damper 32 is open. The third (relief) damper 38 is similarly coordinated such that it mirrors the operation of the first damper 26. So, when the isolation damper 32 is open, the relief damper 38 is closed, and when the isolation damper 32 is closed, the relief damper 38 is open.

The outside temperature sensor 46 of the system is preferably a thermostat, which differs from a sensor in that the sensor transmits information, such as to a control logic board. A thermostat is a mechanically actuated switch, with the mechanical action based on the sensed temperature. A thermostat such as model no 4LZ94A, made by Dayton Temperature Controls Inc. is an example of a suitable thermostat.

The control system disclosed can interact with an existing indoor thermostat, or can operate without connection to the indoor temperature sensor or thermostat. If the outside temperature sensor is a thermostat, the temperature to begin the economizer mode can be set at the outdoor thermostat. It could also be set at the control module in the conditioned space.

FIG. 2 shows a damper which is typical of a damper used in the system herein disclosed. The damper can be cylindrical or rectangular, and in this example it is cylindrical and has crinkled end sections so that it can engage similar end caps of other ducts in the system. This damper is designated as a first damper 26, but each of the other dampers of the system could appear very similar. The diameter of the ducting of this damper, as well as the ducts in this system, would be tailored to a particular installation and cooling and heating requirements. A typical diameter of a duct such as this would be 16 to 20 inches, and it could be 18 to 22 inches long. Inside the first damper 26, is a damper blade 64 which is shown in FIG. 2 in the open position 28. The damper blade 64 has a damper shaft 66, to which the damper blade 64 is attached. Both ends of the damper shaft 66 pivot on bearings connected to the side walls of the damper duct 26. A damper actuator 68 is shown in both FIGS. 2 and 3. The damper actuator 68 receives a signal from the control module to open or close the damper blade 64. An open position damper position sensor 70 is shown in FIG. 2. When the damper blade 64 is in the open position, electrical contact is made at the open damper position sensor 70, and a signal indicating that the damper blade is in the open position is sent to the control module.

In FIG. 3 a closed damper position 30 sensor is shown. When the damper blade 64 is in the closed position 30, electrical contact is made through the closed damper position sensor 72, and a signal is sent to the control module. The open or closed damper position sensors are verified against the operating mode of the HVAC system, whether in economizer mode or non-economizer mode, and a determination is made if the dampers are in the correct position for the selected mode of operation. If they are in the correct position, a signal is shown at the control module, such as a green light. If the dampers are not in the correct position, another visual indicator is activated which indicates an error in damper blade position, such as a red light. A particular installation can have one indicator to indicate all dampers are operating correctly, or it could have individual lights for each damper.

FIG. 4 shows a view of the backside of the control module 20, showing a geometrically coded connector unit 74 which is on the end of a damper cable 50. The coded connector fits in a receptacle 76 which is shaped to receive the electrical connections of the connector, with the receptacle 76 including an orienting structure 78 which engages a similar orienting structure 78 on the connector 74, so that only one orientation of connection is possible. The damper cable 50 connects to the dampers in parallel to deliver the open/close control signal, and in series to provide the circuit used to determine proper damper position. (See Damper Cable diagram X.) This allows any damper to be plugged into any of the connectors at the end of the damper cable 50 while maintaining the path required to support damper status on one input.

FIG. 5 shows a control diagram for the control of the economizing system 10. The control module 20 accepts a user input 80, or override control, which allows a user to direct the HVAC system 10 to allow outside airflow 24 to the conditioned space 18. The control module 20 accomplishes this by providing an outside air activation signal 82 to the first damper 26. The outside air activation 82 signals the first damper 26 to operate in an open damper position 28. The control module 20 not sending an outside air signal 82 to the first damper 26 permits the first damper 26 to operate in a closed damper position 30. The first damper 26 communicates its position either with an open damper signal 84 from the open damper position sensor 70, or a closed damper signal 86 from the closed damper position sensor 72 to a damper position verification module 88. The third (relief) damper 38 is not needed in many older homes. Leakage provides enough pressure relief that the system would work adequately. The second (return) damper could also be excluded in certain installations.

The damper position verification module 88 communicates with the control module 20 the position of the first damper 26, the isolation damper 32, and the relief damper 38 with a single damper position verification signal 90. The control module 20 may be equipped with at least one warning indicator 92, which indicates when any damper is in an erroneous position, i.e., in an off normal position causing malfunctioning. A damper is in an off normal position if it is not operating as directed, which could include, for example: (1) the damper is in neither an open nor a closed damper position; (2) the damper is in a closed position despite receiving a signal to open; or (3) the damper is in a closed position despite receiving a signal to open.

Alternate embodiments can include warning indicators for each damper, to facilitate efficient repair of a malfunctioning damper.

In one such embodiment, if any damper is in an erroneous position, the damper position verification signal 90 indicates as much, and the control module 20 activates a failsafe signal 94, which causes the first damper 26 to switch to a closed position 30. The failsafe signal 94 also causes the isolation damper 32 to open and the relief damper 38 to close. The isolation damper 32 communicates its position to the damper position verification module 88 via a closed damper position signal 96 and an open damper position signal 98. Likewise, the relief damper 38 communicates its position to the damper position verification module 88 via an open damper position signal 100 and a closed damper position signal 102. Correct damper position is reported in series. Any damper not detected in the proper position is detected through the circuit consisting of the switches, damper cable, and control board. The components described above provide continuous feedback of proper damper position. The feature is unique in the HVAC industry in that it provides assurance of proper operation without having to periodically test and inspect the dampers.

FIG. 6 shows a more focused view of a control logic diagram of the disclosed technology. The number references in FIG. 6 have been previously described in the description of FIG. 5, and include a control module 20, an outside air activation signal 82, a first damper 26, open damper position sensors 70, closed damper position sensors 72, a damper position verification module 88, a third (relief) damper 38, an isolation damper 32, a relief damper 38, a damper position verification signal 90.

The disclosed technology thus uses a unique configuration of end switches and wiring harness that provides continuous damper status that is reported by indicator within the conditioned space. Normally 6 digital inputs would be used to verify proper damper position of all 6 operating positions in the three dampers. In the disclosed technology, two series circuits that are further supported by a circuit board which verifies the proper signal is received to match the mode of operation. The disclosed technology uses a single input (from the damper position verification module) to support what would normally require 6 inputs. This reduces the cost of the product. Because this configuration requires a large number of terminations, it could not be easily accomplished in the field by a technician of average skill level. The quick connects and a harness (cables) that provides a portion of the circuit that would be required to configure in the field further allows this system to work given the skills possessed by the average technician. Using hand terminated wiring as in prior art, the damper control and verification circuit without the disclosed technology system would require a minimum of an hour to terminate and would likely be terminated with errors. Using the disclosed system the damper control and verification circuit can be completely and correctly installed in about 1 minute, using four quick connects.

The control module 20 accepts an input 104 from an outside air temperature sensor 46. Based on this input, and a user input 80, the control module 20 directs the operation of the first damper 26, the isolation damper 32, and the relief damper 38. In one embodiment, the control module 20 may also signal and report a temperature sensor error or malfunction 106 if any temperature sensor operates improperly.

In addition, the control module 20 is equipped with a mode display 110 to indicate that the system is operating in the economizer mode 10, that is with the cooling benefit of outside air, or in the non-economizer mode 112. The HVAC system 10 may also provide feedback through a separate display by calculating and displaying the economic benefits of the system, including the run-time, in number of hours, and percentage of total space conditioning that has been provided through free cooling and economizer-supported mechanical cooling.

Further, the HVAC system 10 may provide user further control options as follows. The control module 20 provides the user with a target temperature. The target temperature is the outdoor air temperature at which the system can operate in the economizer mode and provide an economic benefit through economizer-supported mechanical cooling or free cooling. This information enables users, if desired, to activate operation earlier than an automatic system operation might provide. The user simply uses an override control 114 to instruct the control module 20 to send an outside air input 82. The system ON/OFF allows the user to prevent the HVAC system 10 from using any economizing function, relying exclusively on mechanical cooling.

Some embodiments of the disclosed HVAC system include a Logic Box, shown in FIG. 5. The primary purpose of the Logic Box to provide a termination point for all component cabling, and to interpret incoming damper status signals providing a hardwired circuit to prevent operation of the economizer if improper damper position is detected. In addition to this function, in one embodiment the Logic Box also provides circuitry to control the economizer, an LED display output, and a means of enabling and overriding the system. In another embodiment the Logic Box is connected to a separate display/controller providing a more sophisticated user interface to the system. It contains a circuit board and cable specific connectors supporting required terminations. It is connected to the power supply, furnace control board, damper(s), outdoor temperature sensor, and in one embodiment to the separate display/controller.

The functions of the logic box can be combined in one unit, the control module, or can be mounted as a separate unit apart from the control module in the conditioned space. The advantage of splitting the controls into a logic box and a control module is that it allows us to manufacture the product at a much lower price, reduces the number of inputs and outputs required to connect to system devices, (6 inputs are fed into one input to determine damper status,) and allows us the option of utilizing various manufacturers controllers to support future modifications of the product.

While certain exemplary embodiments are shown in the Figures and described in this disclosure, it is to be distinctly understood that the presently disclosed inventive concept(s) is not limited thereto but may be variously embodied to practice within the scope of the following claims. From the foregoing description, it will be apparent that various changes may be made without departing from the spirit and scope of the disclosure as defined by the following claims. 

What is claimed is:
 1. An HVAC and control system for economizer operation, the HVAC system having a power source, a circulation fan, a cooling unit, and a network of air delivery ducts for cooling a conditioned space, the HVAC and control system comprising: an outside air intake duct and a first damper movable between an open and a closed position, with said first damper comprising a damper open position sensor and a damper closed position sensor, with said damper position sensors sensing and signaling a closed or open damper position; an outside air temperature sensor for sensing the temperature of outside air; a control module mounted in said conditioned space with a damper error indicator comprising at least one visual indicator of damper position error, with said control module operationally connected to said power source, said circulation fan and cooling unit, to said first damper, and to said outside air temperature sensor; an economizer mode in which said first damper is opened to allow outside air to be pulled into said HVAC system when said economizer mode is selected, with said selection based on a preselected temperature of outside air or by manual control selection; and a non-economizer mode in which said first damper is closed to prevent outside air from entering said HVAC system when said economizer mode is not selected, with said non-economizer mode selected by outside air temperature being above said preselected temperature or by manual selection.
 2. The HVAC and control system of claim 1 which further comprises an isolation damper positioned in a return air duct, with said isolation damper coordinated with said first damper to operate in an opposite manner as said first damper, with said isolation damper closed when said first damper is open, and open when said first damper is closed, thereby using exclusively outside air for cooling when outside air is at temperature is at or below the user setting, with said isolation damper comprising a damper open position sensor and a damper closed position sensor, with said damper position sensors sensing and continuously signaling a closed or open damper position.
 3. The control system of claim 2 which further comprises a relief damper positioned in said return air duct between said conditioned space and said isolation damper, with said relief damper coordinated with said isolation damper to operate in an opposite manner as said isolation damper, with said relief damper closed when said isolation damper is open, and open said isolation damper is closed, thereby routing air from said conditioned space out of said duct system when said system is using outside air for cooling, with said relief damper comprising a damper open position sensor and a damper closed position sensor, with said damper position sensors sensing and continuously signaling a closed or open damper position.
 4. The HVAC and control system for an economizer system of claim 1 in which said damper position sensors send a continuous feedback of proper damper position to said control module, with said control module displaying a continuous indicator of proper damper position.
 5. The HVAC and control system for an economizer system of claim 1 which further comprises an economizer failsafe signal which is activated when an off normal damper position is detected, preventing operation with improperly positioned dampers, and in one embodiment configured to close said first damper.
 6. The HVAC and control system for an economizer system of claim 1 in which said outside air temperature sensor is configured to activate said economizer mode, by a comparison between said outside air temperature and a user setting.
 7. The HVAC and control system for an economizer system of claim 1 which further comprises a damper cable with a first end and a second end, with said end of said damper cable comprising a plurality of conductors with said damper cable terminated on both ends with geometrically coded connectors, with said control module comprising a corresponding geometrically coded connector for engagement with said first end of said damper cable, and with said second end of said damper cable configured to engage a corresponding geometrically coded connection at said damper(s) with said geometrically coded connectors shaped to prevent misalignments and to allow for error free assembly.
 8. The HVAC and control system for an economizer system of claim 1 which further comprises an isolation damper and a third damper, the isolation damper positioned in a duct between said conditioned space and said outside air intake duct, and said third damper positioned between said conditioned space and said isolation damper, to allow the release of air from the ducting system, with said isolation damper closed and said third damper open in said economizer mode, and with said isolation damper open and said third damper closed in said non-economizer mode.
 9. An HVAC and control system for an economizer system for use with an HVAC system, the HVAC system having a power source, a circulation fan, a cooling unit, and a network of air delivery ducts for cooling a conditioned space, the control system comprising: an outside air intake duct and a first damper movable between an open and a closed position, with said first damper comprising a damper open position sensor and a damper closed position sensor, with said damper position sensors sensing and signaling a closed or open damper position; an isolation damper positioned between said conditioned space and said outside air intake duct, with said isolation damper closed in said economizer mode and with said isolation damper open in said non-economizer mode, with said isolation damper comprising a damper open position sensor and a damper closed position sensor, with said damper position sensors sensing and signaling a closed or open damper position; and a third damper positioned between said conditioned space and said isolation damper, to allow the release of pressurized air from the conditioned space said third damper configured to release overpressure air in said economizer mode, and with said third damper closed in said non-economizer mode, with said third damper comprising a damper open position sensor and a damper closed position sensor, with said damper position sensors sensing and signaling a closed or open damper position; in which each of said damper position sensors send a continuous feedback of proper damper position to said control module, with two damper position signals per damper; an outside air temperature sensor for sensing the temperature of outside air; a control module mounted in said conditioned space with a damper error indicator comprising at least one visual indicator of damper position error, with said control module operationally connected to said power source, said circulation fan and cooling unit, to said first damper by a damper cable, and to said outside air temperature sensor, and with said control module displaying a continuous indicator of proper damper position indicating all dampers are in proper position; said damper cable with a first end and a second end, with said damper cable comprising a plurality of conductors with said damper cable terminated on both ends with geometrically coded connectors, with said control module comprising a corresponding geometrically coded connector for engagement with said first end of said damper cable, and with said second end of said damper cable configured to engage a corresponding geometrically coded connection at said first, second, and third damper with said geometrically coded connectors shaped to prevent misalignments and to allow for quick and error free assembly; an economizer mode in which said first damper is opened to allow outside air to be pulled into said HVAC system when said economizer mode is selected, with said selection based on a preselected temperature of outside air or by manual control selection; and a non-economizer mode in which said first damper is closed to prevent outside air from entering said HVAC system when said economizer mode is not selected, with said non-economizer mode selected by outside air temperature being above said preselected temperature or by manual selection.
 10. The HVAC and control system for an economizer system of claim 9 in which said two damper position signals from each of three dampers are sent to a damper position verification unit, which sends a single damper position signal to said control module.
 11. The HVAC and control system for an economizer system of claim 9 which further comprises an economizer failsafe signal which is activated when an off normal damper position is detected, with said economizer failsafe signal configured to prevent improper operation, and in one embodiment to close said first damper.
 12. The HVAC and control system for an economizer system of claim 9 in which said outside air temperature sensor is configured to activate said economizer mode, by a comparison between said outside air temperature and a user setting.
 13. The HVAC and control system of claim 9 which further comprises a readiness status signal, which is calculated and displayed on said control module, with said readiness status calculated based on outside temperature being sufficient to provide space cooling, and safety conditions determined and configured by system installer being satisfied.
 14. The HVAC and control system of claim 9 which further comprises a sensor monitor for monitoring of temperature sensors and reporting of temperature sensor malfunction, with errors displayed on said control display.
 15. The HVAC and control system of claim 9 which further comprises a calculator of system statistics and a display of system usage and economic benefit, comprising run time and percentage of cooling accomplished by input of outside air.
 16. An HVAC and control system for an economizer system for use with an HVAC system, the HVAC system having a power source, a circulation fan, a cooling unit, and a network of air delivery ducts for cooling a conditioned space, the control system comprising: an outside air intake duct and a first damper movable between an open and a closed position, with said first damper comprising a damper open position sensor and a damper closed position sensor, with said damper position sensors sensing and signaling a closed or open damper position; an isolation damper positioned between said conditioned space and said outside air intake duct, with said isolation damper closed in said economizer mode and with said isolation damper open in said non-economizer mode, with said isolation damper comprising a damper open position sensor and a damper closed position sensor, with said damper position sensors sensing and signaling a closed or open damper position; and a third damper positioned between said conditioned space and said isolation damper, to allow the release of pressurized air from the conditioned space said third damper configured to release overpressure air in said economizer mode, and with said third damper closed in said non-economizer mode, with said third damper comprising a damper open position sensor and a damper closed position sensor, with said damper position sensors sensing and signaling a closed or open damper position; in which each of said damper position sensors send a continuous feedback of proper damper position to said control module, with two damper position signals per damper, with said two damper position signals from each of three dampers are sent to a damper position verification unit, which sends a single damper position signal to said control module; an outside air temperature sensor for sensing the temperature of outside air; a control module mounted in said conditioned space with a damper error indicator comprising at least one visual indicator of damper position error, with said control module operationally connected to said power source, said circulation fan and cooling unit, to said first damper by a damper cable, and to said outside air temperature sensor, and with said control module displaying a continuous indicator of proper damper position indicating all dampers are in proper position; said damper cable with a first end and a second end, with said damper cable comprising a plurality of conductors with said damper cable terminated on both ends with geometrically coded connectors, with said control module comprising a corresponding geometrically coded connector for engagement with said first end of said damper cable, and with said second end of said damper cable configured to engage a corresponding geometrically coded connection at said first, second, and third damper with said geometrically coded connectors shaped to prevent misalignments and to allow for quick and error free assembly; an economizer mode in which said first damper is opened to allow outside air to be pulled into said HVAC system when said economizer mode is selected, with said selection based on a preselected temperature of outside air or by manual control selection; and a non-economizer mode in which said first damper is closed to prevent outside air from entering said HVAC system when said economizer mode is not selected, with said non-economizer mode selected by outside air temperature being above said preselected temperature or by manual selection. 